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Active Control in Mechanical Engineering
Structural Safety 23 (2001) 275–277 www.elsevier.com/locate/strusafe
Book review
Active Control in Mechanical Engineering Louis Jezequel (Editor). A.A. Balkema, 2000, ISBN: 0 90 5809 132 5 This is an interesting volume comprising the papers presented at one of the excellent MV2 conventions in Lyon. Active control is a particularly apt subject for discussion at a time when structures are increasingly required to be lighter and therefore more susceptible to vibration. It is also an essential ingredient in smart structures— another growth area. Interestingly, as I was attempting to make notes on this volume while travelling by train, the level of vibration of the table made it impossible to put pen to paper. Further, the noise from the vibrating seat backs was a constant source of distraction. A number of the contributions in this volume are concerned with rail travel and the impact of vibration on the traveller. The book is divided into six sections: smart materials and structures, new strategies of active control, active isolation systems, active control in rotor dynamics, active control in civil engineering and vibration control. In all, there are 31 contributions. I shall not attempt to precis each paper, rather I will select certain contributions in order to give a flavour of the volume. The first paper in the smart structures section is a review of new damping technologies by Tomlinson. Although this is almost entirely concerned with passive control, it provides an interesting overview of some novel approaches to damping treatment. Traditional constrainedlayer damping is contrasted with new coatings applied using plasma deposition. Also of interest is the description of negative Poisson’s ratio (auxetic) materials and damping layer optimisation using cellular growth models. Another highlight of this section is the paper by Battaini et al. concerning the dynamic behaviour of shape memory alloys (SMA). Again, this is a passive damping application relying on the inherent hysteresis in the material behaviour to dissipate energy. However, the paper both discusses finite element (FE) modelling of SMA bars and shows experimental confirmation of the predictions. The only truly active contribution to this section comes from Bruant et al. who describe the active control of beams. The paper is noteworthy for its treatment of the sensor/actuator locator problem, posed here as an optimisation problem. The second part of the volume—New strategies of Active Control—is, as the title suggests, more concerned with algorithms. The paper by Carmona et al. provides a nice discussion of robust control. The arena is active noise control and the authors present an approach which does not need reference microphones and is furthermore tolerant of uncertain plant. The controller, which is based on robust pole placement, is shown to be effective—particularly in the case of narrow-
276
Book review / Structural Safety 23 (2001) 275–277
band noise. The paper by Perrard et al. here is noteworthy as one of the few contributions based on fuzzy logic. The application problem is to speed and swing control of an overhead crane. As well as demonstrating an acceptable solution, the paper also serves as a compact introduction to fuzzy control. Part three—Active Isolation Systems—is focused firmly on transportation applications, mainly trains. The opening paper by Knolle on bouncing, weaving and pitching in high speed passenger transit systems makes for very interesting reading. It was a surprise to find that high speed trains actually spend most of their time in the air. The discussion encompasses traditional systems— steel wheels on steel rails—and also more modern magnetic levitation systems. This part of the book also contains an interesting review by Bondoux on actuators for active noise and vibration control. Although none of the technologies: electrodynamic shakers, variable reluctance shakers, piezoelectrics are covered in any detail, the comparison given here is useful. The fourth part of the volume is devoted to applications to rotor systems. Here are several contributions from the research group led by Krodkiewski in Melbourne. The first two papers describe a control law based on delayed displacement and velocity feedback. The first paper of the pair describes the theory and demonstrates its use in a simulation of rotor blade control for helicopter flight. The second paper shows how the control law was used to stabilise periodic motions of a laboratory system. Later papers in this part describe an interesting application of an active journal bearing to the control of multi-bearing systems. Civil engineering is the subject of the fifth part of the volume. Here there are discussions of bridges and buildings subjected to earthquake excitation; unfortunately only models are considered. This section is the home of a paper by Battaini and Dyke, which considers the important issue of sensor failure. In this experimental study, two possible courses of action are considered: carry on with the controller designed for the full sensor set, or switch to a controller designed using the reduced sensor network. The authors show that an H2/LQG controller proves to be fairly robust in both cases, but conclude that it is better to use a controller optimised on the surviving sensors. The final part of the book focusses on vibration control. As someone with an interest in nonlinear systems, I found myself drawn particularly to two papers here. The first by Mata-Jimenez et al. is concerned with control of mechanical systems with backlash. The PD control law is demonstrated on a simulated impact damper and proves capable of providing local stabilisation of the closed-loop system around a given periodic orbit. Unsurprisingly, colocated controllers are shown to out-perform non-colocated. The second paper with a non-linear flavour considered the behaviour of systems with gaps under white noise excitation. Actually, this paper was not concerned with control as such, but compared theoretical estimates of various measures with experiment with a good degree of success. Overall then, there is much in this book which is interesting. It is a little disappointing that so many of the papers are not concerned with active control as such and it is an irritation that the degree of editing applied in places appears to have been minimal. However, I enjoyed reading the book, particularly as a researcher who is not primarily concerned with active control, I found it a learning experience. The question arises: who should buy this book? This is difficult. The attendees at the workshop will almost certainly want a permanent record of the proceedings, and I would hope that it will be taken up by libraries. However, I would hesitate to recommend purchase to the general researcher in active control as I am not con-
Book review / Structural Safety 23 (2001) 275–277
277
vinced that its qualities are sufficient to lift it above similar conference proceedings—of which there are many. I do however recommend that you at least inspect a copy and make up your own mind. Keith Worden The Dynamics Research Group, University of Sheffield Department of Mechanical Engineering Mappin Street, Sheffield S1 3JD, UK E-mail address: k.worden@sheffield.ac.uk PII: S0167-4730(01)00015-7
Book review
Active Control in Mechanical Engineering Louis Jezequel (Editor). A.A. Balkema, 2000, ISBN: 0 90 5809 132 5 This is an interesting volume comprising the papers presented at one of the excellent MV2 conventions in Lyon. Active control is a particularly apt subject for discussion at a time when structures are increasingly required to be lighter and therefore more susceptible to vibration. It is also an essential ingredient in smart structures— another growth area. Interestingly, as I was attempting to make notes on this volume while travelling by train, the level of vibration of the table made it impossible to put pen to paper. Further, the noise from the vibrating seat backs was a constant source of distraction. A number of the contributions in this volume are concerned with rail travel and the impact of vibration on the traveller. The book is divided into six sections: smart materials and structures, new strategies of active control, active isolation systems, active control in rotor dynamics, active control in civil engineering and vibration control. In all, there are 31 contributions. I shall not attempt to precis each paper, rather I will select certain contributions in order to give a flavour of the volume. The first paper in the smart structures section is a review of new damping technologies by Tomlinson. Although this is almost entirely concerned with passive control, it provides an interesting overview of some novel approaches to damping treatment. Traditional constrainedlayer damping is contrasted with new coatings applied using plasma deposition. Also of interest is the description of negative Poisson’s ratio (auxetic) materials and damping layer optimisation using cellular growth models. Another highlight of this section is the paper by Battaini et al. concerning the dynamic behaviour of shape memory alloys (SMA). Again, this is a passive damping application relying on the inherent hysteresis in the material behaviour to dissipate energy. However, the paper both discusses finite element (FE) modelling of SMA bars and shows experimental confirmation of the predictions. The only truly active contribution to this section comes from Bruant et al. who describe the active control of beams. The paper is noteworthy for its treatment of the sensor/actuator locator problem, posed here as an optimisation problem. The second part of the volume—New strategies of Active Control—is, as the title suggests, more concerned with algorithms. The paper by Carmona et al. provides a nice discussion of robust control. The arena is active noise control and the authors present an approach which does not need reference microphones and is furthermore tolerant of uncertain plant. The controller, which is based on robust pole placement, is shown to be effective—particularly in the case of narrow-
276
Book review / Structural Safety 23 (2001) 275–277
band noise. The paper by Perrard et al. here is noteworthy as one of the few contributions based on fuzzy logic. The application problem is to speed and swing control of an overhead crane. As well as demonstrating an acceptable solution, the paper also serves as a compact introduction to fuzzy control. Part three—Active Isolation Systems—is focused firmly on transportation applications, mainly trains. The opening paper by Knolle on bouncing, weaving and pitching in high speed passenger transit systems makes for very interesting reading. It was a surprise to find that high speed trains actually spend most of their time in the air. The discussion encompasses traditional systems— steel wheels on steel rails—and also more modern magnetic levitation systems. This part of the book also contains an interesting review by Bondoux on actuators for active noise and vibration control. Although none of the technologies: electrodynamic shakers, variable reluctance shakers, piezoelectrics are covered in any detail, the comparison given here is useful. The fourth part of the volume is devoted to applications to rotor systems. Here are several contributions from the research group led by Krodkiewski in Melbourne. The first two papers describe a control law based on delayed displacement and velocity feedback. The first paper of the pair describes the theory and demonstrates its use in a simulation of rotor blade control for helicopter flight. The second paper shows how the control law was used to stabilise periodic motions of a laboratory system. Later papers in this part describe an interesting application of an active journal bearing to the control of multi-bearing systems. Civil engineering is the subject of the fifth part of the volume. Here there are discussions of bridges and buildings subjected to earthquake excitation; unfortunately only models are considered. This section is the home of a paper by Battaini and Dyke, which considers the important issue of sensor failure. In this experimental study, two possible courses of action are considered: carry on with the controller designed for the full sensor set, or switch to a controller designed using the reduced sensor network. The authors show that an H2/LQG controller proves to be fairly robust in both cases, but conclude that it is better to use a controller optimised on the surviving sensors. The final part of the book focusses on vibration control. As someone with an interest in nonlinear systems, I found myself drawn particularly to two papers here. The first by Mata-Jimenez et al. is concerned with control of mechanical systems with backlash. The PD control law is demonstrated on a simulated impact damper and proves capable of providing local stabilisation of the closed-loop system around a given periodic orbit. Unsurprisingly, colocated controllers are shown to out-perform non-colocated. The second paper with a non-linear flavour considered the behaviour of systems with gaps under white noise excitation. Actually, this paper was not concerned with control as such, but compared theoretical estimates of various measures with experiment with a good degree of success. Overall then, there is much in this book which is interesting. It is a little disappointing that so many of the papers are not concerned with active control as such and it is an irritation that the degree of editing applied in places appears to have been minimal. However, I enjoyed reading the book, particularly as a researcher who is not primarily concerned with active control, I found it a learning experience. The question arises: who should buy this book? This is difficult. The attendees at the workshop will almost certainly want a permanent record of the proceedings, and I would hope that it will be taken up by libraries. However, I would hesitate to recommend purchase to the general researcher in active control as I am not con-
Book review / Structural Safety 23 (2001) 275–277
277
vinced that its qualities are sufficient to lift it above similar conference proceedings—of which there are many. I do however recommend that you at least inspect a copy and make up your own mind. Keith Worden The Dynamics Research Group, University of Sheffield Department of Mechanical Engineering Mappin Street, Sheffield S1 3JD, UK E-mail address: k.worden@sheffield.ac.uk PII: S0167-4730(01)00015-7